Here are detailed instructions for assembly of the speaker testing jig designed HERE.
Please let me finish posting all of the instructions before you contribute or ask a question.

First step is to un-pack the parts. The kit comes with all of the parts inside the enclosure so you will need to loosen the screws to open it. It is not necessary to completely remove the screws. Be careful when removing the cover not to force it and damage either the enclosure or the front panel. The slots that the front and back panel sit in leave very little wood at the edge and this is easily broken. Should you decide to paint or otherwise finish the box, now is the time to do it.

This pic shows the parts and some of the tools needed to assemble the kit:

The "X" on each side of the case show where they line up, just make sure the x on each half are together before screwing the case together again (unfortunately, I didn't do this on the first lot that went out).
Soldering iron, cutters, pliers, solder and I like to use flux on all the pads before I solder them as it makes for a trouble free joint.
A file can be helpful to "fine tune" something but I didn't find I needed it at all here.

The resistors are not marked and it is best to measure them with a multimeter anyway before installing them. The diodes are fairly easy, the larger ones are rectifiers and the smaller ones are zeners. Be careful of the polarity when you are putting them in.

After you have the resistors and diodes in, the board will look like this:

I made a couple of mistakes on these boards. The first is that the holes for the mini jacks are a bit big but it is only an issue on the middle one (it uses the internal switch of the jack). As shown in the pic it needs special attention to solder this one:

Before the boards went out, I scraped some of the soldermask off of the trace to provide some pad area for soldering. Make sure that solder bridges the trace on both sides of the pin. It can be a bit tricky but is doable.
Install the rest of the jacks, including the power jack.

Next you will need some silicone or other type of adhesive to hold the big cap in place:

Bend the leads on the cap (careful to watch polarity) and put some adhesive on the side that faces down. Solder in the cap and take a break while the adhesive cures.

Once that is dry move to the chipamp. Here we see my second mistake: the chipamp needs a washer between it and the back plate. A small aluminum washer (not supplied) would be best but since the amp doesn't put out much power, it never get much more than warm so any kind of metal washer will do. Heatsink compound is not needed here:

Next is to double check your work, look for solder bridges and loose leads. Check the polarity on all of the components again.
It is time to try it. Connect a suitable AC power adapter (12-24VAC, 1 amp) and turn it on. On first turning it on, it will have some DC at the output but this drops after a few seconds (with a speaker connected, it will give a little "pop" and hum for a few second. This hum is normal and will cease - output to the speaker at that time should be dead silent).

Once you have verified that it's not on fire () connect it to your soundcard and give it a test drive: